debug: repeat! stop if Y is too short

another clearer error is thrown later in the code

Author: franckgaga

src/general.jl

@@ -48,6 +48,8 @@ repeatdiag(A, n::Int) = kron(I(n), A)
 function repeat!(Y::Vector, a::Vector, n::Int)
     na = length(a)
     for i=0:n-1
+        # stop if Y is too short, another clearer error is thrown later in the code:
+        na*(i+1) > length(Y) && break 
         Y[(1+na*i):(na*(i+1))] = a
     end
     return Y